FOUS30 KWBC 020828
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
428 AM EDT Thu Oct 2 2025

Day 1
Valid 12Z Thu Oct 02 2025 - 12Z Fri Oct 03 2025

...THERE'S A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE SIERRA, GREAT BASIN AND EASTERN FLORIDA...

...Sierra/Great Basin...
An upper low will dig into the West Coast while sending streams of
vorticity into the Sierra Nevada, Great Basin and Northern 
Rockies. Diffluence will spread across the aforementioned areas 
throughout the day on Friday. At the surface, a low pressure system
will propagate across the interior West, while anomalous moisture 
(3-4 stndv PWATs) streams in behind the preceding cold front. 
Scattered to isolated thunderstorms may develop and produce 
isolated instances of excessive rainfall and flash flooding. 

Upslope enhancement across the Sierra could produce heavier 
rainfall totals than what are currently forecast. EAS probabilities
of 24 hour qpf exceeding 1 inch are over 40% in the Sierra and 
between 15-40% in the Great Basin. Therefore, burn scars over 
central and southern Idaho are at risk of flash flooding today.

...Eastern Florida...
Moist easterly flow into a surface front oriented north-south will
produce scattered convection across Florida today. The surface 
boundary draped along the eastern coast will focus PWATs of around 
2" in that area where MUCAPE between 500-1000 J/Kg will also likely
produce high rain rates. Neighborhood probabilities of exceeding 
5" in 24 hours are between 40-90% from near Miami metro up through 
Melbourne and Orlando.

Kebede


Day 2
Valid 12Z Fri Oct 03 2025 - 12Z Sat Oct 04 2025

...THERE'S A MARGINAL RISK FOR PORTIONS OF THE GREAT BASIN AND
EASTERN FLORIDA...

...Great Basin...
The upper trough propagates through the Great Basin and begins 
lifting north on Friday. The excessive rainfall threat bleeds into
Friday from Thursday as thunderstorms weaken and spread from the 
Great Basin into the Northern Rockies by Friday afternoon. Instability
and moisture will be relatively modest (100-200 J/Kg MUCAPE) 
(0.5-0.9". Ensemble exceedance probabilities of 1" are between 
10-20% over northern Nevada with 2 day totals potentially eclipsing
2" in some places.

...Eastern Florida...
Moisture advection into Florida increases on Friday as a mid-level
circulation embedded within a broader upper ridge continues to
direct moisture and instability into the state's east coast. 
Another inverted surface trough may develop along the state's east
coast and focus convection along the convergence zone. Ensemble 
exceedance probabilities of 2" are between 5-15% along the 
immediate coast, while first guess fields support the marginal with
5% flash flood probabilities.

Kebede


Day 3
Valid 12Z Sat Oct 04 2025 - 12Z Sun Oct 05 2025

...THERE'S A MARGINAL RISK FOR PORTIONS OF SOUTHEAST LOUISIANA AND
EASTERN FLORIDA INTO FAR SOUTHEASTERN GEORGIA...

...Central Gulf Coast...
Mid-level vorticity swirling over the Central Gulf Coast will
generate instability and pull an increasing amount of Gulf 
moisture into the region on Saturday. Convection should fire along 
a coastal convergence zone that develops and diurnal heating should
enhance afternoon/evening storms along that boundary. PWATs will
likely be over 2" with MUCAPE between 500-750 J/Kg. Ensemble exceedance
probabilities of 2" are between 15-30% for much of southeast Louisiana.

...Eastern Florida/Southeastern Georgia...
Tropical moisture associated with Imelda will continue flowing into
Florida due to and upper ridge over the East Coast and embedded
troughing over Florida and the Gulf. A modest instability plume 
should flow up the Florida Peninsula into far southeastern Georgia 
where PWAT's of over 2" and an inverted surface trough could
combine to produce thunderstorms capable of generating 0.75-1"/hr 
rain rates. Ensemble exceedance probabilities of 2" are between 
5-15% along Florida's east coast into southeastern Georgia.


Kebede
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